Subject:
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Re: Wings [was: Re: Building big]
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Newsgroups:
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lugnet.space, lugnet.loc.au
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Date:
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Mon, 25 Jun 2001 10:38:02 GMT
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Reply-To:
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ssgore@superonline.com^ihatespam^
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Viewed:
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1381 times
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David Drew wrote:
>
> Hi.
> I can't remember the density of space off the top of my head, but let's say
> it's somewhere near the 1 molecule per 3m^3 like you suggest. If a vehicle
> is travelling near the speed of light (3*10^8 m/s), then the ship is hitting
> in the vicinity of 1*10^8 molecules per second per metre^2 of frontal
> surface area!
>
> I can't be bothered working out how many molecules of nitrogen and oxygen
> fill a 1m^3 box of air, but I think it can become clear that when travelling
> at near-relativistic velocities, the flow of molecules over the surface of a
> spaceship can become more than high enough to qualify it as a 'fluid', and
> thus impose the problems of drag and turbulence suggested.
>
> later,
> David Drew.
No, it's not..:-) At STP (Standard temperature and pressure, 1atm and
273K if IIRC), only 22.4 lt. of any gas would have 6.022x10^23
molecules. Your number given above is quite negligible when compared to
this I think. You must consider individual attitudes of the molecules in
your case (microscopic approach), rather than their behavior as a whole
as a fluid (macroscopic approach), since there is nothing like you could
mention as a fluid in that case, and continuum model is pretty not
working, which is the most basic thing in fluid mechanics. I might be
wrong about the numbers, it was 12 years ago, but the idea is quite true
I think.
The main problem when traveling through space at such high velocities is
the wear caused by the inter-whatever dust particles that impacting your
ship at similar velocities.
Selçuk
> ----- Original Message -----
> From: "Jason J. Railton" <j.j.railton@cwcom.net>
>
> Oh please. Drag calculations are only approximations for something immersed
> in a fluid. You're not going to get conventional boundary layer effects
> when you only bump into a single gas molecule every few meters. You could
> consider molecular impacts as individual retarding impulses, but if you've
> got enough power to move your own mass that fast, their net effect on
> forward velocity is still going to be negligible. The only concern is their
> net effect on your orientation and course, and that's if you solve the
> problem of the actual damage caused by the impacts.
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Message has 1 Reply:
Message is in Reply To:
 | | Re: Wings [was: Re: Building big]
|
| Hi. I can't remember the density of space off the top of my head, but let's say it's somewhere near the 1 molecule per 3m^3 like you suggest. If a vehicle is travelling near the speed of light (3*10^8 m/s), then the ship is hitting in the vicinity (...) (23 years ago, 22-Jun-01, to lugnet.space, lugnet.loc.au)
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